Alternating current heated thermionic device



Dec. 12, 1933. E, OOSTERHUIS 1,938,636

ALTERNATING CURRENT HEATED THERMIONIC DEVICE Filed Feb. 10, 1930 MMWTMWTWT INVENTOR EKKO 005TERHU\5 BY 7%Wm ATTORNEY Patented Dec. 12, 1933UNITED STATES I ALTERNATING CURRENT HEATED THERIVIIONIC DEVICE EkkoOosterhuis, Eindhoven, Netherlands, assignor to Radio Corporation ofAmerica, a corporation of Delaware Application February 10, 1930, SerialNo. 427,170, and in Germany March 26, 1929 2 Claims.

The present invention relates to thermionic devices, and moreparticularly to improvements in, or relating to, circuit arrangementsfor amplifying valves heated with alternating current.

It is well known that in heating cathodes of thermionic devices toincandescence with alternating current, it is customary to connect thenegative end of the anode circuit to the electrical mid-point of theincandescent cathode. This connection may be established in variousways. One of the best known methods consists in providing the mid-pointof the incandescent cathode with a particular leading-in Wire which istaken through the wall of the tubes.

However, instead of connecting, the real midpoint to the anode circuit,as an alternative the virtual mid-point of the cathode may be connectedthereto. There are various methods of connecting the virtual mid-pointof the cathode. Thus, for example according to a well known method, theanode circuit may be connected to the mid-point of the secondary of thetransformer from which the incandescent cathode is supplied.Alternatively, the terminals of the secondary may have connected acrossthem a resistance, or more broadly an impedancathe mid-point of whichmay be connected to the anode circuit.

The present invention has for its main object a new method of obtainingthe electrical midpoint of the cathode, and consistsin providing thesecondary winding, which is wound in the usual manner, with anadditional coil, the winding direction of the latter being opposed tothat of the secondary winding, and being so large that the free end ofthe said auxiliary coil possesses, for example, the same potential asthe mid-point of the filament.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims, the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically several circuit organizations whereby my invention maybe carried into efiect.

In the drawing,

Fig. 1 shows an arrangement embodying the invention,

Fig. 2 shows the arrangement applied to a thermionic device having anindirectly heated cathode.

Referring to the drawing in which like reference characters in thedifferent figures represent the same elements, in Fig. 1 is shown atriode having its cathode 1 heated by a source of alterhating current,the secondary 2 of the transformer T, having a coil 3 connected with it,the

coil 3 being in the anode circuit of the tube. This auxiliary coil iswound in a direction opposite to that of coil 2. Furthermore, the coil 3is so proportioned that the free end 1 of the coil possesses the samepotential as the electrical mid-point of the cathode 1.

The second coil 3 may be made of thin wire as no substantial currentstrength occurs therein. There is thus obtained the advantage that it isnot necessary that the secondary winding 2 which is of thick wireshouldbe tapped at its .mid-point. The additional coil 3 may beproportioned (at will) so that the potential of the free end 4 is equalat all times to that of a suitable point of the incandescent cathode 1.

The invention is shown applied in Fig. 2 to tubes having an indirectlyheated cathode 1. In this case the cathode is connected to the free end4 of the additional coil 3. By the use of a thin wire for the additionalcoil the proportions of the transformer are not increased.

While I have indicated and described several systems for carrying myinvention into effect, it will be apparent to one skilled in the artthat my invention is by no means limited to the particular organizationsshown and described, but that many modifications in the circuitarrangements, as well as in the apparatus employed may be made without.departing from the scope of my invention as set forth in the appendedclaims.

What I claim is:

1. In combination, an electron discharge tube including a heaterelement, a cathode, an anode and a grid, a source of pulsating heatingcurrent, a transformer between the element and the source, an auxiliarycoil having one end connected with the transformer secondary and beingwound in a direction opposite'to the latter, said cathode beingconnected to the other end of said coil.

2. In combination, an electron discharge tube including a heaterelement, a cathode, an anode and a grid, 2. source of pulsating heatingcurrent, a transformer between the element and the source, an auxiliarycoil having one end connected with the transformer secondary and beingwound in a direction opposite to the latter, said cathode, anode andgrid being connected to the other end of said coil.

EKKO OOSTERHUIS.

